The present invention relates to wireless communication, and more particularly, to a timing method for a mobile station in a wireless communication system and related devices.
As wireless communication system technology progresses, wireless communication and personal mobile communication have become an essential portion of daily life for a great number of persons. Among various kinds of wireless communication specifications, the third generation wireless communication specification has become popular because of integrating various functionalities such as voice communication, message service, and even audio/video and text data transmission.
Please refer to FIG. 1 illustrating a diagram of a wireless communication system 10. The wireless communication system 10 includes a plurality of cells (not shown in FIG. 1) provided with communication service by a plurality of base stations. Because the plurality of cells are usually adjacent to one another, this kind of wireless communication system is usually referred to as a cellular wireless communication system. For simplicity, only a single cell 12 is illustrated as an example in FIG. 1, wherein the cell 12 is covered in the communication service by the base station 14.
In the serving area of the cell 12 shown in FIG. 1, a mobile station 16 is also illustrated. The mobile station 16 usually includes an antenna 18 for transmitting and receiving wireless communication signals; a lower layer 20 for processing data related to communications between the mobile station 16 and the base station 14 through the antenna 18; and an upper layer 22 usually including elements such as a processor and a memory, for communicating with the base station 14 through the lower layer 20 and the antenna 18 to construct a communication network. Since the mobile station 16 herein locates at the serving range of the cell 12, the mobile station 16 will select the cell 12 as a serving cell.
According to various kinds of wireless communication specifications in the 3rd Generation Partnership Project (3GPP), standards describing which elements in a wireless communication system should respectively reach a working time thereof are defined in detail. Many of the standards are involved with calculations of maximum time limitations. For example, the 3GPP TS 05.08 specification defined in the 3GPP for radio subsystem link control of the cellular wireless communication system defines that within a period of thirty seconds, a mobile station should check the Base Station Identification Code (BSIC) for each carrier out of Broadcast Control Channel (BCCH) carriers of non-serving cells (also referred to as neighbor cells) relating to the recent six strongest receiving power levels. This ensures that the mobile station is still monitoring the same cell. The specification also defines that within a period of five minutes, a mobile station should decode a BCCH data block of each carrier out of the BCCH carriers of non-serving cells relating to the recent six strongest receiving power levels. The BCCH data block includes parameters that will influence a cell reselection operation of each carrier out of the BCCH carriers of non-serving cells relating to the recent six strongest receiving power levels. In order to reach the timing in the wireless communication system 10 mentioned above, it is common to use system resources of the mobile station 16 to generate at least one timer. For example, the system resources used to generate the timer could be the operation bandwidth of a processor and the storage volume of a memory, both located in the upper layer 22. As shown in FIG. 1, in order to perform checking of the BSIC for each carrier out of six BCCH carriers, the mobile station 16 must generate six first timers 17a-17f corresponding to the six BCCH carriers, respectively. Please note, the timing period of each first timer is assumed to be thirty seconds herein. Similarly, in order to perform decoding of the BCCH data block to derive the parameters for the cell reselection operation, the mobile station 16 must generate six second timers 19a-19f corresponding to the six BCCH carriers, respectively. The timing period of each second timer is assumed to be five minutes herein.
Furthermore, as processing power of the mobile station 16 of the prior art is limited, the lower layer 20 thereof is only capable of checking the BSIC corresponding to one neighbor cell at a time. For the same reason, the lower layer 20 is only capable of decoding the BCCH data block corresponding to one neighbor cell at a time.
Thus, using the method mentioned above, the mobile station 16 in the wireless communication system 10 must generate a dedicated timer corresponding to each carrier to achieve the functionality of timing calculations for each of the above-mentioned actions (e.g. the action of checking the BSIC or the action of decoding the BCCH data block) that needs timing operation in the mobile station 16. As a result, a lot of system resources of the mobile station 16 are occupied and therefore the working efficiency is influenced.
Additionally, as the period of the action of checking the BSIC and the period of the action of decoding the BCCH data block are controlled using the first timers 17a-17f and the second timers 19a-19f, respectively, the action of checking the BSIC and the action of decoding the BCCH data block are not synchronized. Therefore, if any frequency error occurs between the serving cell and one of the neighbor cells, it is possible to introduce timing drift, resulting in failure of decoding the BCCH data block.